The invention relates to a device for inspecting contact-sensitive planar materials or work-pieces, e.g. wafers for the semiconductor industry, solar cells, glasses, FPD substrates, or biologically active substrates for biosensors, as well as materials having contact-sensitive curved surfaces. In the following, every kind of material or work-piece will be denoted as material. The surfaces of materials will be treated in different working steps, wherein treatment shall be understood to be working steps like vapor-deposition or structuring, for example. Afterwards, the result of treatment will be inspected. Inspection can be carried out by using a camera provided with an image recognition and evaluation program.
Technologies assigned for the treatment of the top surface and also of the bottom surface of the materials require both these surfaces to be inspected. The top surface of material can be inspected easily, as the material is positioned on an inspection table or a conveyer belt so that there is a free view onto the top surface thereof. However, it is very difficult to inspect the bottom surface of material at the same time, as this surface is at least partly covered by sections of the support structure so that e.g. a camera is not capable of scanning all of this surface.
For example, when a solar cell the bottom surface thereof being very sensitive to mechanical contact is transported, this solar cell is borne by several small conveyer belts. Therefore, only those areas of the bottom surface of the solar cell, which are not covered by the conveyer belts, can be inspected by a camera from below. However, when the total bottom surface of the solar cell is to be inspected, the solar cell must be removed from the conveyer belt, turned and again put onto the conveyer belt, but this is time-consuming and susceptible to trouble with continuously running processes.
In order to solve these problems, according to the prior art, the transport path is subdivided into several segments separated from each other by gaps so that the material is delivered up by the single segments. As the material is not supported at the transfer gap, the total width thereof can be scanned. However, when the material to be transported is insufficiently stiff, there is the problem that the transfer gap has to be dimensioned very small. Now and then, it is not possible to perform scanning in an unhindered way.